Many rare-earth chelate compounds exhibit bright, narrow band fluorescence when illuminated with ultraviolet light. Thermal activation of a radiationless decay channel in some of these compounds causes the quantum yield of this fluorescence to exhibit a dependence on temperature. Thus, fluorescence micrographs of thin films of such materials contain information about the temperature field or profile of the surface of the underlying substrate which can be extracted by conventional image processing techniques. This technique can have high (sub-micron) spatial resolution as well as superior temperature sensitivity and resolution.
The aforementioned technique is particularly useful in the fabrication, testing and evaluation of solid state electronic devices whereby measurement of the temperature profiles during operation of the device is utilized as a quality control to detect elements operating below specification, as indicated by an abnormal temperature profile. It is also useful in obtaining temperature profiles of the surface of biological bodies and for the determination of the temperature of the surface of a body having a uniform temperature.
Details of the application of rare-earth chelate films for this purpose and the mode of operation, methods and apparatus embodying this technique can be found by reference to U.S. Pat. Nos. 4,455,741 and 4,819,658 issued to Paul R. Kolodner on Jun. 26, 1984 and Apr. 11, 1989, respectively, which patents are incorporated herein by reference. The particular films taught in those patents are films of EuFOD and EuTTA doped in a polymethylmethacrylate matrix. These films are suitable for obtaining temperature profiles near or above room temperature.